This invention relates to a method of and an electronic sewing machine for producing pattern patterns with stitches by varying relative position between a needle and a fabric to be sewn. The sewing machine is of the type which includes a rotary upper drive shaft coupled to the needle so as to reciprocate vertically the needle within a maximum swinging range while a fabric feeding device transports the fabric, thus forming zig-zag stitches.
To embroidering stitches, such patterns as shading, vignette, graduation or the like are significant and interesting for making stitched patterns soft, smooth, cubic or solid (called this as mainly "shaded pattern" after). When shaded stitches are formed as in the embroidery stitch, such a pattern as shown in FIG. 1 is desired which is appropriately at random in needle amplitude position and is not clear in periodicity. However, for producing such desired patterns automatically, a huge capacity of memory has been required for storing needle amplitude data.
According to the invention, when pattern data are read out from a pattern data memory which stores a plurality of different ordinary patterns, each of the memory locations is accessed in such a manner that an address signal (code) is prepared at random with respect to a desired pattern. When the shaded stitches are to be formed the random address signal prepared for the desired pattern is used as the stitch data of the shaded pattern. Each of the stitch data of the shaded pattern employs a part of the data used just before the stitch as data which form the shaded stitch, whereby the stitch always moves over the center of the full amplitude of the needle, so that the stitches are made at random for forming the shaded pattern, and may be easily controlled.